KR20070066467A - Artificial soil composition for the greening and method of manufacturing the same - Google Patents

Abstract

Provided are a method for preparing an artificial soil composition for tree-planting, and the artificial soil composition prepared by the method to improve the water absorption by capillary, cation exchange power and tree-planting power. The artificial soil composition comprises a composition which comprises 20-60 parts by weight of sewage sludge, 1-5 parts by weight of a CaO-based frit, 20-40 parts by weight of clay, 1-5 parts by weight of calcium carbonate and 1-5 parts by weight of carbon black; and a porous sinter which is applied on the surface of the composition. Preferably, the porous sinter comprises gamma-alumina. The artificial soil composition is sintered under reductive gas atmosphere after the porous sinter material is coated.

Description

Artificial soil composition for greening and its manufacturing method {Artificial soil composition for the greening and method of manufacturing the same}

1 is an explanatory diagram showing a manufacturing process of the artificial soil composition of the present invention,

Figure 2 is a thermal process schedule table of the present inventors artificial soil composition,

3 is a scanning electron micrograph showing the microstructure of the artificial soil composition of the present invention,

Figure 4 is a graph showing the movement of pore distribution of the artificial soil composition of the present invention.

The present invention relates to an artificial soil composition for greening and a method of manufacturing the same. More specifically, after the sewage sludge is made of a shaped body as a main raw material, the inside of the molded body is sufficiently carbonized to form micropores, and the surface of the molded body is oxidized to form a porous sintered body to form an internal carbide layer in bulk form. It is to make a protective artificial soil composition for greening.

At the same time, a large amount of waste and sludge are emitted from home and industrial fields.

These wastes and sludges that are inevitably discharged are only partially treated and recycled, but a considerable amount is left unattended or illegally discarded or accumulated over time, causing serious social and environmental problems. .

For example, in the case of sewage sludge, landfilling has been banned in recent years, and sea dumping under international convention is also banned, so the problem of treating sewage sludge becomes an environmental and industrial problem.

When manufacturing a zeolite using such sewage sludge, an import raw material such as pearlite is often added, and other supplements are often used in parallel.

Here, pearlite is a swelled pearl rock (volcanic stone) 4-12 times its original volume at a high temperature of about 760 ~ 1200 ℃, it is used for breeding, planting, plug production and transplantation, indoor landscaping, etc. It is used a lot in.

On the other hand, there are also methods for mixing sewage sludge calcined powder as it is, artificial agricultural soil, but the weight is not light weight, there is a problem of lack of porosity and strength.

The problem of this prior art is as follows.

First, in the manufacture of sewage sludge with artificial soil composition, according to the foaming process by the prior art firing, it is possible to obtain a pore size belonging to a relatively coarse region of about 1 ~ 100㎛. This is helpful in terms of securing a light weight, but the microporosity is less developed, the lack of the most necessary properties for artificial soil for greening, such as adsorption force by capillary force, cation exchange capacity (CEC).

Second, the carbonization process by the reducing atmosphere of the prior art also shows a relatively good adsorption characteristics, but the carbide produced by the prior art is 90% or more fine powder (fine powder), the bulk granulated carbide in less than 10% It is only. Therefore, strength also has a weak disadvantage.

For reference, in case of artificial soil for greening, it must maintain a certain strength and particle size to be used for growing (particle size about 0.5 ~ 2mm) and drainage (particle size about 2 ~ 8mm). Therefore, bulk form granulation is essential to ensure permeability.

Therefore, the product carbonized sewage sludge in the prior art has a low effective permeability coefficient, easy to be suspended or lost during rainfall (rainwater), and has a low strength, which is not suitable for the use of artificial soil for greening.

The present invention aims to provide an artificial soil composition having excellent greening performance, such as the ability to develop micropores by internal carbonization and protect the internal carbonization layer by an external coating treatment, such as capacitive absorption and cation substitution ability.

Furthermore, it aims at recycling environmental wastes and solving environmental problems.

The manufacturing method of artificial soil composition for greening of the present invention is 20 to 60 parts by weight of sewage sludge, 1 to 5 parts by weight of CaO frit, 20 to 40 parts by weight of clay, 1 to 5 parts by weight of calcium carbonate and 1 to 5 parts by weight of carbon black. Mixing and molding a composition comprising parts; Coating a porous sintered body on the surface of the molded body; And sintering the coated molded body in a heat treatment apparatus in which a reducing gas is injected.

In the present invention, the coating step, it is preferable to coat the gamma alumina on the surface of the molded body.

The present invention preferably further includes a step of quenching and discharging the sintered body after the sintering step.

The artificial soil composition for greening of the present invention comprises 20 to 60 parts by weight of sewage sludge, 1 to 5 parts by weight of CaO frit, 20 to 40 parts by weight of clay, 1 to 5 parts by weight of calcium carbonate and 1 to 5 parts by weight of carbon black. It is preferable that a porous sintered body is formed on the surface of the composition.

Hereinafter, the artificial soil composition for greening of the present invention will be described in detail through the manufacturing process of the present invention.

The present invention has the technical features of operating parallel and mutually opposite reduction and oxidation processes. As a result, a molded article having a predetermined shape is formed, and the inside of the molded article is sufficiently carbonized to secure micropores, and the surface of the molded article is oxidized to form a porous sintered compact to protect the internal carbide layer in a bulk form. .

Herein, internal carbonization refers to carbonization of an organic material contained in 90% or more of sewage sludge by heat treatment in a reducing atmosphere or an oxygen free atmosphere. This is a technology that maximizes the amount of carbides by depleting oxygen and burning organic matter. By such internal carbonization, fine pores are well developed in the molded body, and properties such as absorbency and cation substitution ability are improved.

However, it is difficult to make a molded article having a diameter of 2 to 8mm, the strength is very low, and there are many fine powders, which make it difficult to use artificial soil.

In general, the process of sintering the formed body by heat treatment is carried out in air, and the sintering (firing) takes place in an actual oxidizing atmosphere due to the inflow of much oxygen.

Most of the organic matter inside the molded body is volatilized and disappeared, and other inorganic components remain to be heat treated. At this time, a large number of large pores are generated, it is possible to manufacture a molded article having a high strength and light weight.

However, due to the loss of many organic matters, the amount of the final product is small, the energy consumption is large, and the size of the internal pores is large, so the characteristics such as absorption by the micropores, cation exchange capacity is weak.

The artificial soil composition for greening of the present invention has a technical feature in that the reduction and oxidation process in parallel to overcome the above-mentioned disadvantages.

It burns organic materials at high temperature and short-term firing to lighten them, but only burns organic materials to the extent that light weight of less than about 1 density can be used as artificial soil for greening, and the remaining organic materials are reduced as much as possible, and carbides with fine pores It is characterized by remaining.

More specifically described as follows.

By inserting the molded body at a high temperature, the organic material on the surface of the molded body is volatilized first. In the meantime, some 2-100cc / min species also flow some reducing gas to make a partial reducing atmosphere rather than a complete reducing atmosphere. For this reason, oxygen does not go to the inside of the molded body, so a reducing atmosphere is formed inside the molded body.

That is, since the firing time is shortened and rapidly injected at a high temperature, the molded body swells due to the volatilization of moisture and organic matter inside the molded body. Due to the mixing of some reducing gas in this process, oxygen does not flow into the molded body, but only heat is transferred. As a result, the inside of the molded body is carbonized, and the outside is oxidized and light in weight. The carbide inside the molded body and the porous sintered body outside are strongly bound physically and chemically.

Accordingly, the internal carbonization improves characteristics such as micropores, water absorption rate, and cation substitution ability, and secures minimum light weight and strength by external lightweight foaming and firing.

Hereinafter, look at the technical features of the present invention through the manufacturing process.

First, look at the blending process.

Stir and mix a composition comprising 20 to 60 parts by weight of sewage sludge, 1 to 5 parts by weight of CaO based flits, 20 to 40 parts by weight of clay, 1 to 5 parts by weight of calcium carbonate and 1 to 5 parts by weight of carbon black. .

If the sewage sludge is less than 20 parts by weight, the amount of organic matter is small, and the light weight effect due to foaming is not expressed. If the sewage sludge is more than 60 parts by weight, the sintered body bursts due to overexposure, which is not suitable. Therefore, it is preferable that 20-60 weight part of sewage sludges are added.

When CaO-based flits (frit) is added 1 to 5 parts by weight, it may serve as a sintering aid and structure strengthening agent. In addition, CaO: Al ₂ O _{3 :} SiO ₂ It is preferable to have a composition ratio of = 0.5-1: 1-2: 1-2.

When 20 to 40 parts by weight of clay is added, it is mixed with sewage sludge to facilitate the production of shaped bodies having a certain shape. As the clay used in the present invention, various kinds of clays such as montmorillonite, bentonite, and illite may be used.

When 1 to 5 parts by weight of calcium carbonate and carbon black are added, the foaming power of the molded body can be improved. Calcium carbonate increases the amount of open pores on the surface, and carbon black (1-100 nm) helps to form fine pores.

Next, look at the molding process.

The molded article of the composition can be produced in various shapes as needed. In particular, the pellet-shaped molded article has a feature of easy mass production, but when clay having a high viscosity is added, the pellet-shaped molded article is easily formed. Normally, spheres and cylindrical pellets having a diameter of 1 to 8 mm are prepared.

Next, look at the coating process.

The surface of the molded body is coated with gamma alumina (γ-alumina). The coated gamma alumina melts at a slightly higher temperature than the components of the shaped body, a mixture of sewage sludge and clay. This suppresses the phenomenon that the surface of the molded article introduced into the high temperature and short-term firing process melts and the pores are clogged. That is, gamma alumina can maximize carbide production by securing the porosity of the surface of the molded body and increasing the melting point temperature therein.

In addition, since gamma alumina itself is a material having a lot of pores, even when coated on the surface of the molded body, it does not cause any problem to escape the organic matter inside the molded body.

Next, look at the sintering process.

The heat treatment apparatus may be a conventional equipment such as tubular or rotary kiln. Air and a reducing gas such as N ₂ or Ar are mixed and supplied into the heat treatment apparatus.

In this case, the amount of air and reducing gas can be adjusted using a valve, etc., and the reducing gas is supplied at about 2-100 cc / min. When the amount of reducing gas is supplied exceeding 100 cc / min, it is reduced excessively and the foaming force of the sintered compact becomes weak. When the amount of reducing gas is supplied at less than 2 cc / min, the degree of carbonization decreases, making it difficult to produce carbide therein. Therefore, the amount of reducing gas is preferably supplied 2-100cc / min.

The reaction conditions are sintered at 650 to 900 ° C. for 10 to 30 minutes. If it is less than 650 degreeC, there exists a problem of foaming force fall and strength weakening. If it exceeds 900 ℃ there is a problem that the internal pores are clogged due to the partial melting phenomenon caused by the high temperature. Therefore, the reaction temperature is preferably 650 to 900 ° C. And in order to burn only a fixed amount of organic substance in a molded object, reaction time is 10 to 30 minutes is preferable.

Next, look at the discharge process.

In the sintering process, the greater the amount of foam of the molded product, the greater the shrinkage occurs during the cooling process should be noted. In addition, when the glass component is formed due to the high glassy temperature or the high firing temperature of the components of the molded body, the strength during quenching is sharply lowered, so care should be taken.

Therefore, in order to introduce a quenching process, it is preferable that it is a baked product like this invention, and is fully porous.

Therefore, the outlet of the heat treatment apparatus, for example, is equipped with a water-cooled plate of aluminum material having high thermal conductivity, such that the sintered body is cooled more quickly, thereby preventing shrinkage of the sintered body in the cooling process.

1 is an explanatory diagram showing a manufacturing process of the artificial soil composition of the present invention, Figure 2 is a thermal process schedule table of the artificial soil composition of the present invention. Hereinafter, referring to Figures 1 and 2, it will be described in more detail the manufacturing method of the artificial soil composition of the present invention through one embodiment of the present invention.

<Example>

Sewage sludge cake 53kg, Cao frit 3kg, clay 40kg, carbon black 3kg, and other 1kg into a mixer and stirred. Molding is carried out in pellet shaped bodies having a diameter of 1 to 8 mm.

Gamma alumina powder is evenly applied to the surface of the molded body, and carbonized and sintered at a temperature of 850 ° C. for 20 minutes while the surface is properly dried. At this time, the reducing gas is injected to 60 cc / min.

Thereafter, the sintered body is quenched through a water cooling plate, and the particle size is separated into 2 mm and 5 mm to prepare an artificial soil composition.

3, 4 and Table 1, Table 2 is the data calculated from the artificial soil composition prepared by the above embodiment.

Figure 3 is a scanning electron micrograph showing the microstructure of the artificial soil composition of the present invention. As shown in FIG. 3, significant pores were observed and the plasticity of the skeleton was also good. Since the inside is not easily detached and separated physically, there is no sign of performance degradation due to loss, and excellent pressure resistance of about 80ton / m ² is expressed in a good sintered state. In addition, due to such porosity, considerable absorption rate and light weight can be obtained.

Table 1 below is a heavy metal hazard test result table of the artificial soil composition of the present invention. Through this, it can be seen that the results for all the heavy metal dissolution is stable.

Constituent (ppm) Artificial soil Soil quality standard CD 2.2 4 Cu 3.4 125 As 0.9 15 Hg ND 10 Pb 1.6 300 Cr ^{6 +} 0.09 10

Figure 4 is a diagram showing the pore distribution movement phenomenon of the artificial soil composition of the present invention.

The artificial earth A is foamed only by the general foaming and sintering process, and the artificial earth B is applied in parallel with the carbonization process. As shown in FIG. 4, when the carbonization is performed in parallel, the pore region moves to the right side, which is a microregion, through which the micropores are considerably developed. It can be seen that it affects the size more than the quantitative change of the pore. This is the effect of carbide remaining inside.

Both A and B artificial soils are basically bimodal in their porosity in porous materials produced by foaming.

Here, the bimodal form refers to the pore distribution form generally shown in porous products. There are two peaks on the graph, where the micropores and the large (relatively large) pore areas are separated so that they are clearly visible.

In the case of B artificial soil, pores of about 0.05 μm in size are considered to be volatilized to the surface of the organic material and pores in the porous alumina framework, and relatively fine pores of 0.005 μm in size are considered to be pores present in the inner carbide layer.

Table 2 below is a performance test evaluation table comparing the artificial soil composition of the present invention with general open ground (masato), and the results of soil performance measurement of particles of about 2 mm or less for plant growth.

Evaluation item unit Noji (Masato) Development Artificial earth Porosity (capacity) % 30-40 50 Permeability coefficient mm / h 1200 To 2000 Bobby Org. C (g / kg) 8.4 28.8 Effective Moisture Rate vol% 24 28 Thermal conductivity kcal / mh ?? -0.1 -0.05 density g / cm3 1.5 to 1.7 0.7 to 0.8 Pressure resistance ton / m2 48 52 pH - 6.3 7.4 Heavy metal elution ppm - - CEC meq / 100g 7.3 14

Comparing the performance of only artificial soil without additives, it shows a performance that can be sufficiently used as artificial soil for greening. In particular, it shows superiority in items, such as a biboiling force (a long-lasting force), a cationic substitution ability (CEC), and a pressure resistance. In addition, the physical and physicochemical characteristics change little with the passage of time.

The characteristics of the artificial soil composition for greening of the present invention is summarized as follows.

First, in the materialization of sewage sludge into artificial soil, it overcomes the disadvantages of existing technologies such as sludge carbonization technology and foaming technology by plastic foaming.

Second, sewage sludge, which is a waste, is used as the main raw material. In the process of plastic foaming, the inside of the molded product is carbonized and the surface is sintered. In addition, since the internal carbide and the outer coating surface are strongly bound to each other physically and chemically, there is no deterioration in long-term performance due to separation or separation.

Third, it can replace the import of lightweight material for greening, which depends on the total amount of import.

Fourth, it is possible to reduce the sludge discharged from the sewage treatment plant to 1/5 to 1/10.

Fifth, heavy metals and the like are solidified in the high temperature heat treatment step, and are environmentally stable.

Sixth, it is economical to use waste resources that can utilize waste treatment expenses to reduce production costs.

The present invention has the effect of excellent greening performance, such as the ability to absorb the capillary force, cation substitution ability by the development of micropores by the internal carbonization, and by protecting the internal carbide layer by the external coating treatment.

And by recycling the waste sewage sludge, there is an effect of environmentally friendly treatment of sewage sludge.

Claims (11)

Mixing and forming a composition comprising 20 to 60 parts by weight of sewage sludge, 1 to 5 parts by weight of CaO-based frit, 20 to 40 parts by weight of clay, 1 to 5 parts by weight of calcium carbonate, and 1 to 5 parts by weight of carbon black; Coating a porous sintered body on the surface of the molded body; And And sintering the coated molded body in a heat treatment apparatus in which a reducing gas is injected. Method for preparing artificial soil composition for greening. The method of claim 1, In the mixing and forming step, the CaO-based frit has a composition ratio of CaO: Al 2 O 3: SiO 2 = 0.5 ~ 1: 1 ~ 2: 1 ~ 2 Method for preparing artificial soil composition for greening. The method of claim 1, The coating step, characterized in that for coating the gamma alumina on the surface of the molded body Method for preparing artificial soil composition for greening. The method of claim 1, The sintering step, characterized in that the reducing gas is injected into the heat treatment apparatus 2-100cc / min Method for preparing artificial soil composition for greening. The method of claim 1, The sintering step is carried out at a temperature range of 650 ~ 900 ℃ Method for preparing artificial soil composition for greening. The method of claim 1, The sintering step is characterized in that it is carried out for 10 to 30 minutes Method for preparing artificial soil composition for greening. The method of claim 1, After the sintering step is further characterized in that it further comprises the step of sintered body is quenched and discharged Method for preparing artificial soil composition for greening. The method of claim 7, wherein In the discharging step, it is quenched using an aluminum water cooling plate Method for preparing artificial soil composition for greening. The porous sintered body is formed on the surface of the composition comprising 20 to 60 parts by weight of sewage sludge, 1 to 5 parts by weight of CaO-based frit, 20 to 40 parts by weight of clay, 1 to 5 parts by weight of calcium carbonate and 1 to 5 parts by weight of carbon black. Characterized by Artificial soil composition for greening. The method of claim 9, The CaO-based frit has a composition ratio of CaO: Al 2 O 3: SiO 2 = 0.5-1: 1: 1-2: 1 Artificial soil composition for greening. The method of claim 9, The porous sintered body is made of gamma alumina, characterized in that Artificial soil composition for greening.

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